Chen Lei, Wang Mingpeng, Huang Li, Zhang Zhaojie, Liu Fanghua, Lu Guangtao
State Key Laboratory for Conservation and State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, The Key Laboratory ofMinistry of Education for Microbial and Plant Genetic Engineering, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China.
Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Yantai, China.
BMC Microbiol. 2017 Jun 27;17(1):142. doi: 10.1186/s12866-017-1056-9.
The phytopathogenic Xanthomonas campestris pv.campestris is a gram-negative bacterium and the causal agent of black-rot disease of cruciferous crops. Many gram-negative bacteria possess a family of proteins, called Dsbs, which are involved in disulfide bond formation in certain periplasmic proteins. In our preliminary screening of the virulence to the plants we identified that gene XC_0531 which annotated gene dsbD of Xanthomonas campestris pv. campestris (Xcc) is related to the virulence to the host plants.
Here, we found XC_0531 encoded a DsbD like protein. Its deletion is sensitive to DTT and copper, decreased accumulation of free thiols in periplasm. Its deletion also affected heme synthesis, position of Soret band and the production of peak c550. This suggests that XC_0531 is related to c-type cytochromes biogenesis. XC_0531 mutation decreased the utilization of different carbon sources (such as galactose, xylose, maltose, saccharose and glucose), reduced extracellular polysaccharide (EPS) production, decreased extracellular enzyme activities (protease, cellulose and amylase), slowed down growth rate of Xcc and weakened virulence to the plants. These results suggest that these phenotypes caused by XC_0531 mutation is possibly due to deficient biosynthesis of c-type cytochromes in respiration chain and the formation of disulfide bonds. Our work confirmed the function of XC_0531 and provide theory basis for scientists working on molecular mechanisms of cytochrome c biogenesis, pathogenesis of Xcc, development of EPS commercial values and protecting plant from black rot.
We confirmed the function of gene XC_0531, which encodes a DsbD like protein, a protein correlated with c-type cytochrome biogenesis. This gene is related to the virulence to plants by affecting funtion of cytochromes c and probably disulfide bonds modification of proteins in type II secretion system (T2SS).
植物病原野油菜黄单胞菌野油菜致病变种是一种革兰氏阴性细菌，也是十字花科作物黑腐病的病原体。许多革兰氏阴性细菌拥有一类名为Dsbs的蛋白质家族，它们参与某些周质蛋白中二硫键的形成。在我们对植物毒力的初步筛选中，我们发现注释为野油菜黄单胞菌野油菜致病变种（Xcc）的dsbD基因的XC_0531基因与对宿主植物的毒力有关。
在这里，我们发现XC_0531编码一种类似DsbD的蛋白质。其缺失对二硫苏糖醇（DTT）和铜敏感，会减少周质中游离硫醇的积累。其缺失还影响血红素合成、Soret带位置和c550峰的产生。这表明XC_0531与c型细胞色素的生物合成有关。XC_0531突变降低了对不同碳源（如半乳糖、木糖、麦芽糖、蔗糖和葡萄糖）的利用，减少了胞外多糖（EPS）的产生，降低了胞外酶活性（蛋白酶、纤维素酶和淀粉酶），减缓了Xcc的生长速度并削弱了对植物的毒力。这些结果表明，由XC_0531突变引起的这些表型可能是由于呼吸链中c型细胞色素生物合成不足和二硫键形成所致。我们的工作证实了XC_0531的功能，并为研究细胞色素c生物合成的分子机制、Xcc的致病机制、EPS商业价值开发以及保护植物免受黑腐病侵害的科学家提供了理论依据。
我们证实了基因XC_0531的功能，该基因编码一种类似DsbD的蛋白质，一种与c型细胞色素生物合成相关的蛋白质。该基因通过影响细胞色素c的功能以及可能影响II型分泌系统（T2SS）中蛋白质的二硫键修饰而与对植物的毒力有关。
